Goat Island Light was first established in 1822, then rebuilt in 1859. The 25 foot brick tower originally had a fifth-order lens, but has been automated with a 300mm optic. It's still and active aid to navigation, but the Coast Guard leases the island to the Kennebunkport Conservation Trust.
You can view the light from the lobster company docks at the entrance to Cape Porpoise Harbor, just up the road from Kennebunkport. While you're there, get yourself a great lobster roll and sit out on the dock.